1. Field of the Invention
This invention relates to devices that attach a door handle to a spindle on a lock mechanism to prevent the handle from being removed. More specifically, this invention relates to catch assemblies that prevent the handle from being removed when the lock mechanism is in the locked state and allow the handle to be removed when the lock mechanism is in the unlocked state.
2. Description of Related Art
Door locks are typically provided with a catch assembly that prevents the outer handle from being removed from the outer spindle when the door is locked. A conventional catch assembly includes a spring loaded catch oriented perpendicular to the spindle on the lock. The catch can be pressed inward when the door is unlocked to allow the base of the handle to slide over the catch and on or off the spindle. A retaining opening, such as a hole or slot to match the catch, is formed in the base of the handle perpendicular to the spindle. As the handle slides into position on the spindle, the retaining opening reaches alignment with the catch, allowing the catch to spring outward and engage the handle.
The handle cannot be removed until the catch is again pressed to the inward position. The retaining opening extends through the handle base so that the catch can be disengaged. Provided that the door is unlocked, the catch can be pressed inward against its spring pressure by inserting a tool into the retaining opening from the outside to apply inward pressure against the end of the catch.
When the door is locked, however, a lock element moves underneath the bottom end of the catch to prevent the inward motion necessary to remove the handle. This prevents the catch from being disengaged from the retaining opening in the handle base and thereby prevents the handle from being removed while the door is locked.
Although this system is quite effective, and is very widely used in bored lock designs, it is susceptible to a determined brute-force attack. The security of the catch assembly depends upon the strength of the catch and the support of the underlying lock element to prevent the catch from being driven inward. There are specialized tools available to locksmiths that can apply extreme force to the catch through the retaining opening in the handle base. The force available is sufficient to axially collapse the catch and/or crush the underlying lock element that supports the catch against inward motion. The catch is thereby forced out of engagement with the handle base, allowing the handle to be removed even though the lock mechanism remains in the locked state. Removing the handle allows access to the lock mechanism, which may permit the locked door to be opened.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a catch assembly for retaining a handle on a spindle that provides increased resistance to brute-force attacks.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.